Sound amplifier



F 'iled NQV. 12, 19 28 ATTORNEf Patented June 17, 1930 UNITED STATES ROBERT F. TACK, OF NEW YORK, N. Y.

SOUND AMPLIFIER Application filed November 12, 1928. Serial No. 318,833.

My invention relates to the art of sound transmission and, more particularly, my invention relates to amplification of sounds received in a telephone instrument.

The invention consists in the combination With a telephone instrument of an exponentially developed sound passage for amplifying the sound received and also in the amplifier horn having such a characteristic sound passage.

By using a sound passage of cross section exponentially developed I am able to so greatly amplify the sound received that a person can clearly hear the sound in the amplifier at a distance of several feet permitting him the free use of the hand which otherwise would hold the receiver to the ear. Thus the person listening may be making notes or glancing through a file while listening or waiting to listen.

The invention is illustrated by means of the accompanying drawing on which Fig. 1 shows an amplifier horn and telephone receiver in accordance with the invention; and

Fig. 2 a combination of the amplifier horn and a telephone set on a common base.

The amplifier horn 10 (Fig. 1) is mounted on a base 11 suitable for positioning on a desk or table. The base 11 has a padded socket 12 arranged to receive a receiver 15 of telephone set as shown. The receiver is placed over the inlet of sound passage 13 so that the sound is directed into the passage.

The sound passage has a continuously increasing cross-sectional area in the direction of sound flow, being developed in accordance with the exponential equation S=S .E

S represents the area of a cross-section at any distance a: measured along the center.

line of the sound passage from the source of sound, which may be assumed to be two tenths of an inch above the inlet opening of the sound passage.

S represents the area of the inlet crosssection of the sound passage.

on is a constant which can be evaluated by substitution in the formula of the chosen total length and terminal cross-section.

E is the value of the base of the Napierian system of logarithms, namely 2.718.

m is the distance along the center line from the source of sound.

In a horn reduced to practice in accord ance with the invention, applicant has chosen one half inch as the inlet diameter. The out let diameter of this horn is three and one quarter inches. The horn does not employ any mechanical contrivance for amplifying sound, but merely by using the exponential ly derived cross-section, the sound is amplified so greatly as to make a device of the kind practical.

I am aware that the use of a horn to amplify the sound emitted from a telephone re ceiver is known, but such horns have previously been failures. I am also aware that exponentially developed sound passages have previously been proposed. However, none, prior to me, has combined these features and made a telephone receiver amplifier with a sound passage of exponentially derived cross-section and it is by making the horn in this manner that I accomplish unusual and unexpected results.

'I prefer the form of horn shown on the drawing having the form of the letter C but it will be readily understood that many different forms may be used in carrying the invention into practice.

Fig. 1 is intended to represent the horn as independent of the transmitter of the telephone set, this arrangement permitting the horn to be placed remotely on a desk or table while the mouthpiece can be conveniently near the person. i

In Fig. 2 the horn and complete telephone set including the transmitter 17 have a common base 16.

The device may be made of any suitable metal or other material such as aluminum, wood, phenol aldehyde products or papier mach and, where necessary, the material may be made waterproof in any known way.

It will be understood that the invention is not limited except by the terms of the apreceiver and having 7 a sound passage of cross section increasing in accordance with the equation 8 8 .17?

2. An amplifier horn comprising a base portion and a vertically extending portion, said base portion having a seat for-holding the receiver of a' telephone instrument, and said horn having a sound: passage of cross-section increasing in accordance with the equation S=S .E and extending downwardly from said seat, Within the base portion and up wardly in the Vertically extending portion.

3. An amplifier horn comprising a'base' portion and a vertically extending portion, said base portion having a seatfor holding a telephone receiver in inverted vertical, position, and said horn having a sound passage of cross-section increasing in accordance with the equation S=S .EF and extending vertically downwardly, curving within the base, extending upwardly within the verti cally extending portion and having an outlet flaring toward the horizontal.

' ROBERT F. TACK. 

